The control of bile acid conjugation will be explored by studying the enzymic processes involved in the formation of amino acid conjugates of bile acids. Enzymes catalyzing the formation of the bile acid:CoA intermediate and enzymes active in the acylation of amino acids by this intermediate will be isolated and purified. Enzyme acitvity will be characterized by kinetic technics and species dependent differences will be sought. In vivo studies of the role of the enterohepatic circulation in regulation of enzyme activity will be studied in animal models as well as the effect of pharmacologic manipulation of bile acid conjugation.